Modern turbines often operate at extremely high temperatures. The effect of temperature on the turbine blades and/or stator vanes can be detrimental to the efficient operation of the turbine and can, in extreme circumstances, lead to distortion and possible failure of the blade or vane. In order to overcome this risk, high temperature turbines may include hollow blades or vanes incorporating so-called impingement tubes for cooling purposes.
These so-called impingement tubes are hollow tubes that run radially within the blades or vanes. Air is forced into and along these tubes and emerges through suitable apertures into a void between the tubes and interior surfaces of the hollow blades or vanes. This creates an internal air flow for cooling the blade or vane.
Normally, blades and vanes are made by casting having hollow structures. Impingement tubes may be inserted into the hollow structure from one or other end and usually welded with the hollow structure to fix them in place. Problems arise when a size of an impingement cooling zone and thus the region of the aerofoil with the highest cooling efficiency, is limited by the size of the opening through which the impingement tube is inserted into the aerofoil or the blades or vanes, respectively.
From EP 1 380 725 A2 it is known to embody the impingement tube as different box- or shell-shaped bodies. These bodies are all of a size approximately but no larger than an opening to insert said bodies into a chamber of a blade or vane and are inserted successively through said opening.
U.S. Pat. No. 4,798,515 A discloses a turbine assembly comprising a basically hollow aerofoil and a wall segment (fixed trunnion support portions) arranged at a side of the hollow aerofoil oriented basically perpendicular to a span wise direction of the hollow aerofoil. An insertion aperture is recessed in said wall segment providing access to the hollow aerofoil.
An impingement tube of the turbine assembly is positioned in the hollow aerofoil via a trunnion. Flared resilient portions of the impingement tube are braced or force fitted into an inlet aperture of the trunnion. The trunnion is located within the hollow aerofoil via trunnion mounted portions mating the wall segment, i.e. the fixed trunnion support portions.
It is desirable to provide a method for assembling an impingement tube in a hollow aero-foil of an aerofoil-shaped turbine assembly such as turbine rotor blade and stator vane which the above-mentioned shortcomings can be mitigated, and especially a more aerodynamic efficient aerofoil and gas turbine component is facilitated.
It is further desirable to provide an advantageous aerofoil-shaped turbine assembly such as a turbine rotor blade and a stator vane. It is also desirable to provide an advantageous impingement tube used in such an assembly for cooling purposes.